Placentation

Structure – Function

Rob Foster

VetReproPath.com Circle of Reproductive Life*

Genital pathology Diseases of Sexual Oestrus Cycle Conception Development Embryonic ‘From the day we arrive on the Perinatal planet mortality And blinking, step into the sun mortality There's more to be seen Birth than can ever be seen Attachment More to do than can ever be done’ Stillbirth *

Fetal development Abortion, Maceration, Mummification * “Circle of Life” Music by Elton John, lyrics by Tim Rice, Performed by Elton John Housekeeping

◼ Continuing Education ◼ Zachary: Pathologic Basis of Veterinary Disease ◼ Reproductive Pathology Website

◼ Presentations ◼ Available on CourseLink and vetrepropath.com ◼ Conventions of File Naming standardised ◼ Accessible - Accessibility of Ontarians with Disabilities Act (AODA)

◼ Accessibility checking limits font size (22 point) and amount of material on slides (5-6 lines) ◼ Notes (aka long notes) are on CourseLink. ◼ Read before the lecture Placenta - human/primate speak

◼ ‘A flat cake’ = disc = exchange area

◼ ‘Membranes’ = transparent membranes

Photo complements of common.wikimedia.org Reproduction

Reproduction occurs at the interface between aquatic and terrestrial environments. What do you need?

◼ Protective environment

◼ Shock absorbing

◼ Oxygen, Nutrition

◼ Transfer maternal immunity

◼ Waste removal

Gastric brooding frog: American Museum of Natural History Grey Nurse and Great White Sharks

Complements of Australian Museum Online australianmuseum.net.au Lamniform Sharks – Nurse Shark

◼ Young develop in the uterus in an egg case

◼ When 55mm long, break out

◼ Nutrition of young

◼ Uterine fluid (histotrophic nutrition)

◼ Oophagy – eat unfertilized eggs

◼ Cannibalism – eat other fetuses

◼ 2 are born! Chicken and the egg Chicken and egg – Which came first?

Complements of www.urbanext.uiuc.edu Mammals

◼ Amniotes (membrane around the fetus) – tetrapod vertebrates including amphibians, reptiles, mammals

◼ Mammals

◼ Prototheria – Monotremes

◼ Theria

◼ Metatheria – Marsupials

◼ Eutheria – placental mammals Basic embryology

Zygote = fertilised ovum Morula = 16 cells +

Blastula = blastema and blastocoel

Blastocyst Formation of Chorion Chorion = Trophoblasts + mesoderm

Inner cell mass Trophoblasts

Trophoblasts are in contact with the mother Formation of endoderm

◼ Endoderm = gut + yolk sac

Future fetus

Future chorion Future Fetus

Future Gut

Chorion Formation of Yolk sac

Fetus

Gut

Chorion Yolk sac Formation of Amnion

Fetus

Gut

Chorion Yolk sac Formation of amnion Amniotic sac

Fetus Gut

Chorion Yolk sac Formation of allantois

Amniotic sac Fetus Gut

Chorion Yolk sac Allantois Formation of allantois

Amniotic sac Fetus

Chorion

Yolk sac Allantois Formation of allantois

Membranes Amniotic sac Amniotic membrane Fetus

Chorioallantoic Umbilical cord = urachus, 2 arteries membrane Yolk sac Allantois 1 vein

Vascular system of placenta

◼ Blood supply is high volume – low pressure

◼ Yolk sac prominent placentas

◼ Marsupials

◼ Rodents and lagamorphs

◼ Carnivores

◼ Allantoic vasculature takes over later Horse

Endometrial surface with embryo

Photo courtesy Dr Tony Hayes Horse

Photo courtesy Dr Tony Hayes Horse

Photo courtesy Dr Tony Hayes Placental structures

◼ Chorion and arrangement

◼ Pig – villus – uterine milk - histotroph

◼ Equine – microcotyledonary – uterine milk - histotroph

◼ Ruminant – cotyledonary - haemotroph

◼ Carnivore – zonary - haemotroph ◼ Allantoic cavity and membrane ◼ Amniotic cavity and membrane ◼ Umbilical cord and components Umbilical cord

◼ 2 arteries – from iliac arteries

◼ 1 vein – to ductus venosis

◼ Urachus – from bladder to allantois Porcine placenta

Chorionic cysts Porcine placenta Villi Equine placenta Equine placenta

Uterus Microcotyledonary

Endometrial glands

Chorioallantois Chorioallantois Ruminants – placentomes

◼ Caruncle (maternal) ◼ Cotyledons (fetal)

www.fungiforays.co.uk Ruminant Placentome

Uterus Caruncle

Cotyledon

Chorioallantois Ruminants Cotyledonary Carnivore

Zonary (girdle) Labyrinth

Marginal hematomas on each side of labyrinth Remnants

◼ Meckels diverticulum – small intestine – yolk sac

◼ Yolk sac remnant in horse

◼ Persistent urachus

◼ Round ligaments of bladder (umbilical arteries)

◼ Falciform ligament (umbilical vein) Placental structures

◼ Chorion and arrangement

◼ Pig

◼ Equine

◼ Ruminant

◼ Carnivore ◼ Allantoic cavity and membrane ◼ Amniotic cavity and membrane ◼ Umbilical cord and components